Road vehicle electrical system with transducers detecting faults and producing unique outputs operating a receiving and display unit

ABSTRACT

A fault detecting system for a road vehicle includes a plurality of fault transducers, each producing its own unique output in the event of a fault. The receiving and display unit is operable by these unique outputs for indicating each fault, and a single cable is used to connect all the transducers to the receiving and display unit.

United States Patent Ives [ 1 May 23,1972

[54] ROAD VEHICLE ELECTRICAL SYSTEM WITH TRANSDUCERS DETECTING FAULTSAND PRODUCING UNIQUE [56] References Cited OUTPUTS OPERATING A RECEIVINGAND DISPLAY UNIT UNITED STATES PATENTS [72] Inventor; Andrew p [vesSolihull, England 3,431,779 3/ 1969 Wilken et al ..340/52 R [73]Assignee: Joseph Lucas (Industries) Limited, Birprimary Examiner JOhn wCaldwell mingham' gland Assistant Examiner-Glen R. Swann, Ill 22 Filed:Aug. 25, 1970 Stem [2 1] Appl. No.: 66,699 [57] ABSTRACT A A faultdetecting system for a road vehicle includes a plurality [30] ForeignApplication Priority Data of fault transducers, each producing its ownunique output in the event of a fault. The receiving and display unit isoperable Aug. 26, 1969 Great Britain ..42,455/69 by these unique outputsfor indicating each fault and a single cable is used to connect all thetransducers to the receiving [52] US. Cl. ..340/52 F, 180/103, 307/10 Rand display unit I [51] Int. Cl ..B60q l/00 [58] Field of Search .340/52F, 52 R, 66, 414, 412, 3 Claims, 4 Drawing Figures I k l3 a b c d lZ it\2 I2 Patented May 23, 1972 lNVENTOR ATTORNEYS Patented May 23, 1972 4Sheets-Sheet 5 2% Ww mM w Patented May 23, 1972 3,665,384

4 Sheets-Sheet 4.

INVENTOR Mad @112 Km A TQRNEYS ROAD VEHICLE ELECTRICAL SYSTEM WITHTRANSDUCERS DETECTING FAULTS AND PRODUCING UNIQUE OUTPUTS OPERATING ARECEIVING AND DISPLAY UNIT BACKGROUND OF INVENTION This inventionrelates to a fault detecting system for road vehicles.

Where warning devices are provided in a road vehicle for indicatingvarious faults, the complexity of the vehicle wiring harness increases,and since different types and numbers of faults are indicated ondifferent vehicles it becomes difficult to provide a single harnesssuitable for more than one vehicle. The object of the invention is tominimize this difficulty.

SUMMARY OF THE INVENTION A system according to the invention comprises aplurality of fault transducers each producing its own unique output inthe event of a fault, a receiving and display unit operable by saidunique outputs for indicating each fault, and a single cable connectingall the transducers to the receiving and display unit.

The system specified above enables a single wiring harness to be used invehicles having widely difierent fault detecting systems. For example,on a vehicle where only two faults are to be detected, then twotransducers would be used, both transducers being coupled to the singlecable and fed to a receiving and display unit having two stages for thetwo faults respectively. Using the same harness on a vehicle on whichfour faults are to be detected, then all that is necessary is to use areceiving and display unit with four stages, and to employ fourtransducers which are coupled to the receiving and display unit throughthe same single cable.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings,

FIG. 1 is a block diagram illustrating one example of the invention, and

FIGS. 2 and 3 are circuit diagrams illustrating parts of two receivingand display units, and

FIG. 4 is acircuit diagram illustrating a further example.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a roadvehicle includes a battery having one terminal earthed and a supply line11 connected to the live battery terminal through the ignition switch 9of the vehicle. The battery voltage is held substantially constant by aconventional regulator, but in addition the voltage on the line 11 isaccurately controlled by a separate regulator shown at 8. It is desiredto monitor four faults on the vehicle, and for this purpose four faulttransducers 12a, 12b, 12c and 12d are provided at appropriate positionson the vehicle, the transducers being-connected between the line 11 andearth. The form of the transducers is not important, as long as theyprovide an electrical output when the fault occurs, and as long as theoutput from each of the four transducers is different.

The line 11 is further connected to a reference generator 13, whichsupplies four signals to the four stages 14a, 14b, 14c, 14d, of areceiving and display unit 14 having lamps or other indicators a, to15d, which are operated by the stages 14a to 14d respectively. Theoutput terminals of the transducers 12a to 12d are connected to a singlecable 16 which provides an input to each of the stages 14a to 14d. Byvirtue of the input signal received from the generator 13, each of thestages 14a to 14d responds to an output from the transducers 12a to 12drespectively, so that if a fault occurs resulting in an output from thetransducers 12a, then the stage 14a operates to energize the indicator15a. Likewise, outputs from transducers 12b, 12c and 12d result inenergization of indicators 15b, 15c and 15d respectively.

The block diagram is of course considerably simplified, and as thus fardescribed simultaneous outputs from all four transducers would result inenergization of all four indicators. As a practical matter, however, themost convenient reference to provide is a voltage level, so that forexample, the generator 13 impresses on the four stages 14a, to 14ddiscrete voltage levels with the stage 14a having the smallest voltageand the stage 14d the largest voltage. The transducers 12a to 12d canthen readily be made to produce respectively four voltage levels, thehighest level being obtained from the transducers 12d. However adifficulty then arises in that the output from the transducer 12d ispotentially capable of operating all four stages 14a to 14a, whichclearly would be incorrect. For this reason, in the preferred embodimentin which the references are voltage levels, the stages 14a to 14d arecoupled so that when a given stage is operated, it prevents operation ofall stages which are capable of operating at lower voltages. Thus, ifthe transducer 12d produces an output, it operates the stage 14d toenergize the indicator 15d, but at the same time the stages 14a to 14are prevented from energizing their indicators 15a to 15c. This in turnmeans that if two faults occur at once, only the fault which causes thehigher voltage to beimpressed on the line 16 will be indicated, and forthisreason the transducer associated with the most serious fault isarranged to impress the largest voltage on the line 16, and thetransducer with the least serious fault impresses the lowest voltage onthe line 16.

The way in which the inhibition on various stages of the unit 14operates will be clearer from the more detailed examples of the unitshown in FIGS. 2 and 3.

Referring now to the example shown in FIG. 2, the lines 11 and 16 arethe same as those shown in FIG. 1, and in addition there is an earthline 17 and a positive supply line 18 connected to the vehicle batterythrough the switch 9. Connected in series between the lines 11, 17 are apair of resistors 19, 21 the junction of which is connected to the baseof an n-p-n transistor 22 having its emitter connected to the line 17through a resistor 23 and its collector connected to the emitters of apair of n-p-n transistors 24, 25. The collectors of the transistors 24,25 are connected to the line 11 through re sistors 26 and 27respectively, the base of the transistor 25 is connected to the line 16,and the base of the transistor 24 is connected to the referencegenerator 13 shown in FIG. 1.

The collector of the transistor '25 is connected to the base of a p-n-ptransistor 28, the emitter of which is connected to the line 11, and thecollector of which is connected to the emitter of another p-n-ptransistor 29, the transistor 29 having its collector connected to theline 17 through resistors 31, 32 in series. The junction of theresistors 31, 32 is connected to the base of an n-p-n transistor 33, theemitter of which is connected to the base of an n-p-n transistor 34having its emitter connected to the line 17. The collectors of thetransistors 33 and 34 are connected through a warning lamp 35 to theline 18.

The components thus far described form one stage of the receiving anddisplay unit, which contains one stage for each fault transducer. Twofurther stages are shown in FIG. 2, and are indicated with the referencenumerals already used increased for the next stage by and for the thirdstage by 200. It will be noted that the base connection of thetransistors 122 and 222 are made to the single resistance chain 19, 21which can be used for all three stages. It will also be observed thatthe base of the transistor 29 in the first stage is connected to thecollector of the transistor 124 in the second stage, and

similarly the base of the transistor 129 in the second stage isconnected to the collector of the transistor 224 in the third stage. Thetransistor corresponding to the transistor 29 in final reference voltageapplied to the base of the transistor 24 is selected so that the longtailed pair constituted by transistors 24 and 25 will occupy its statewith transistor 24 conducting until a one volt signal appears on thebase of transistor 25, at which point the long tailed pair will bedriven to its alternative state. Likewise, the long tailed pair 124, 125will switch at 2 volts, and the long tailed pair 224, 225 will switch at3 volts. When there is no signal on the line 16, the transistor 24 isconducting, the emitter current flowing through the transistor 22.The'transistor 25 is oh and so no base current is supplied to thetransistor 28. Thus, the transistor 28 is off, as are the transistors 33and 34 which are connected as a Darlington pair. The lamp 35 is off, andsimilarly the lamps 135 and 235 are off.

Assume that a l volt signal appears on the line 16, then neither longtailed pair 124, 125 or 224, 225 is affected. However, the signal turnson the transistor 25, so that base current now flows in transistor 28which turns on. Current also flows by way of resistor 123, transistor122 and transistor 124 to the base of transistor 29 to turn transistor29 on, so that current can flow throughtransistors 28 and 29 and theresistor 31 to turn on the transistors 33 and 34 and energize the lamp35.

Assume now that the line 16 receives a 2 volt signal. The lamp 135 willnow be energized in the manner just described for the lamp 35. Thetransistor 25 will turn on as before, and provide base current to thetransistor 28. In this case, however, the transistor 29 cannot turn onbecause the connection .of its base to the line 17 is broken by theturning off of transistor 124 in the second stage. Consequently, thelamp 35 is not energized.

If a 3 volt signal appears on the line 17, the lamp 235 will turn on,but although the transistor 125 conducts, transistor 129 cannot turn onbecause its path to the line 17 is blocked by non-conduction oftransistor 224. Similarly, although lamp 135 is not illuminated, thesecond stage has still operated so that transistor 124 is off, andconsequently no base current is supplied to transistor 29, which remainsoff so that lamp 35 remains off.

It will be appreciated that since there is no need to inhibit the laststage by way of the transistor 229, the transistor 229 of this stage canbe omitted altogether, with the collector of the transistor 228connected directly to the upper end of the resistor 231.

Turning now to the example shown in FIG. 3, the lines 11, 16, 17 and 18are the same as those shown in FIG. 2. Connected in series between thelines 11, 17 are a pair of resistors 41, 42 the junction of which isconnected to the base of an np-n transistor 43 having its emitterconnected to the line 17 through a resistor 44 and its collectorconnected to the emitters of a pair of n-p-n transistors 45, 46 thecollectors of which are connected to the line 11 through resistors 47,48 respectively. The base of the transistor 46 is connected to the line16, and the base of the transistor 45 is connected to the referencegenerator 13. The collector of the transistor 45 is connected to thebase of a p-n-p transistor 49, the emitter of which is connected to theline 11, and the collector of which is connected through a pair ofresistors 51, 52 in series to the line 17. The

collector of the transistor 49 is further connected to the collector ofa pn-p transistor 53 having its emitter connected to the line 11, andthe junction of the resistors 51, 52 is connected to the base of ann-p-n transistor 54 having its emitter connected to the line 17 and itscollector connected through a resistor 55 to the line 18. The collectorof the transistor 54 is also connected to the base of an n-p-ntransistor 56, the

are interconnected by coupling the base of the transistor 53 to thecollector of the transistor 146. Similarly, of course, the base of thetransistor 153 is connected to the collector of the transistor 246 andso on.

When there is no signal on the line 16, the transistor 45 is on and thetransistor 46 is off. Current flows through the resistor 44, transistor43 and transistor 45 to turn on the transistor 49, so that base currentis provided to the transistor 54, which holds the transistors 56 and 57off so that the lamp 58 is not energized. Similarly the lamps 158 and258 are not energized.

If a 1 volt signal appears on the line 16, assuming the same values asin FIG. 2 are being employed, then the transistors 145 and 245 will stayon, but the transistor 46 will turn on and the transistor 45 turn off toremove the base current from transistor 49, so that transistor 54 turnsoff and current flowing through the resistor 55 turns on the transistors56 and 57 to'energize the warning lamp 58. If a 2 volt signal appears onthe line, the lamp 158 is illuminated, but although the transistor 49turns off, the transistor 53 is turned on as a result of conduction ofthe transistor 146, and current flows through the transistor 53 to holdon the transistor 54 so that the transistors 56 and 57 stay off.Similarly, if a 3 volt signal appears on the line, the lamp 258 will beilluminated, but transistors 153 and 53 will both be on, therebyensuring that lamps 58 and 158 are off.

Referring now to FIG. 4, there are provided positive and negative supplylines 61, 62 fed by the vehicle battery. The lines 61 and 62 areinterconnected through a resistor 63 and the collector-emitter path of atransistor 64 in series, the transistor 64 having its base and collectorinterconnected, and its collector further connected to the base of ann-p-n transistor 65. The emitter of the transistor 65 is connected tothe line 62, and its collector is connected through resistors 66 and 67respectively to the emitters of n-p-n transistors 68 and 69, thecollectors of which are connected through resistors 71 and 72respectively to the line 61. The collector of the transistor 68 isfurther connected to the emitter of a p-n-p transistor 73, the base ofwhich is connected to the collector of the transistor 69 and thecollector of which is connected to the anode of'a diode 74. Thecollector of the transistor 69 is connected to the emitter of a p-n-ptransistor 75 having its base connected to the collector of thetransistor 68 and its collector connected to the anode of a diode 76.The diodes 74 and 76 have their cathodes connected to the line 62through resistors 77, 78 in series, and the junction of resistors 77 and78 is connected to the base of an n-p-n transistor 79, the emitter ofwhich is connected to the line 62 and the collector of which isconnected through a resistor 81 to the line 61. The collector of thetransistor 79 is further connected to the base of an n-p-n transistor 82having its emitter connected to the base of an n-p-n transistor 83, theemitter of which is connected to the line 62 through a warning lamp 84.The collectors of the transistors 82 and 83 are connected to the line61.

The circuit illustrated in the drawing is duplicated for each transducerin the system, and the transistor 69 has its base connected to a biasingcircuit 85 providing a predetermined bias to the base of the transistor69, whilst the transistor 68 has its base connected to a lead 86 whichis equivalent to the common line 16 in FIGS. 1 to 3.

In operation, assuming that none of the transducers of the system isproducing an output, then the transistor 69 conducts but the transistor68 is non-conductive. Current flowing through the transistor 69 turns onthe transistor 73, which provides a signal by way of the diode 74 toturn on the transistor 79, so that the transistors 82 and 83 are off andthe lamp 84 is extinguished. Suppose now by way of example that thearrangement shown is set to operate at a voltage level of 5 volts,corresponding to a particular fault. If another fault occurs impressingon the line 86 a voltage of less than 5 volts, then the transistor 68can conduct but the transistor 69 will conduct more heavily than thetransistor 68, so that the diode 74 is still conducting and the lamp 84is off. If a fault occurs which impresses on the line 86 a largervoltage than the 5 volts for which the arrangement is designed, then thetransistor 68 will conduct more than the transistor 69, and in this casethe transistor 75 will be conductive, and current flowing through thediode 76 will turn on the transistor 79, keeping the lamp 84extinguished. Only if the signal on the line 86 is the signalrepresenting the fault for which the circuit shown is designed will thetransistors 68 and 69 conduct equally, in which case both transistors 73and 75 will be off, and there will be no current flow through eitherdiodes 74, 76 so that the transistor 79 is off, and the transistors 82and 83 conduct to turn on the lamp 84. It will of course be appreciatedthat with this system a number of similar stages can be employed set towork at different voltages, and there is no need to provide anyinterconnection between the stages to prevent more than one stage frombeing operated by a given voltage level.

It will be appreciated that the voltage discriminators described aboveare stated to operate at a specific voltage, but

in practice they will be designed to operate over a small voltage rangedetermined by the components 71, 66 and 72, 67, to allow for tolerancesin other component values.

Having thus described my invention what l claim as new and desire tosecure by Letters Patent is:

l. A fault detecting system for a road vehicle, comprising a pluralityof fault transducers each producing in the event of a fault an output inthe form of a voltage level, each of said transducers producing adifferent voltage level, so that the output produced by each transduceris unique, a receiving and display unit operable by said unique outputfor indicating each fault, and a single cable connecting all thetransducers to the receiving and display unit.

2. A system as claimed in claim 1 in which the receiving and displayunit includes a plurality of voltage-sensitive switching circuits, eachof which is sensitive to a small voltage range so that only one of theswitching circuits is operated by a given voltage on said single cable.

3. A system as claimed in claim 1 in which the receiving and displayunit includes a plurality of switching circuits each of which requires aminimum voltage to cause it to operate, so that a given voltage levelcorresponding to a given fault operates its own switching circuit, butis also capable of operating the switching circuits which can beoperated by lower voltage levels, the switching circuits beinginterconnected so that for a given voltage level, operation of theswitching circuit which can be operated by lower voltage levels isprevented.

1. A fault detecting system for a road vehicle, comprising a pluralityof fault transducers each producing in the event of a fault an output inthe form of a voltage level, each of said transducers producing adifferent voltage level, so that the output produced by each transduceris unique, a receiving and display unit operable by said unique outputfor indicating each fault, and a single cable connecting all thetransducers to the receiving and display unit.
 2. A system as claimed inclaim 1 in which the receiving and display unit includes a plurality ofvoltage-sensitive switching circuits, each of which is sensitive to asmall voltage range so that only one of the switching circuits isoperated by a given voltage on said single cable.
 3. A system as claimedin claim 1 in which the receiving and display unit includes a pluralityof switching circuits each of which requires a minimum voltage to causeit to operate, so that a given voltage level corresponding to a givenfault operates its own switching circuit, but is also capable ofoperating the switching circuits which can be operated by lower voltagelevels, the switching circuits being interconnected so that for a givenvoltage level, operation of the switching circuit which can be operatedby lower voltage levels is prevented.